I have a golden pothos plant growing on a moss stick. It's about 90cm tall and in a 20cm pot. I have never repotted it and I'm thinking it really needs it now. The moss stick has become wobbly so I have to rest it against the wall for it to stand straight. The plant is doing very well and has grown a lot, but I am a bit unsure how to repot it. Do I buy a deepish pot and bury more of the moss stick in the compost to steady it? And do I cut off the leaves from the bottom - so as not to bury the leaves? I've never repotted a big plant before. Any help would be appreciated, thanks!
Better not to bury it (the plant) any deeper than it is now. More soil against the stem(s) is not good.
If the stake is rotting off inside the pot then there is not much you can do to stabilize it. If the plant roots are attached to it, then you will want to try, however. Perhaps figure out a way to attach a new stake to the moss stick and stick that new one in the soil.
For a plant that is tall, then a wider pot is more stable. You might look for one that is just a little deeper, but a lot wider.
Another way to stabilize the moss stake would be to attach it to the wall with some kind of removable material so that you can move the plant for cleaning or whatever, then put it back and re-attach the stake to the wall.
Example: A cup hook in the wall and a bit of wire to make a loop.
Ditto most of the above, except for attaching to the wall. You want to be able to freely rotate the plant so that it will not end up with all the leaves "looking out the window." In all probability, the big post is rotted off under the soil, but it's no real problem. Get a package of long bamboo stakes from the plant store, and put in as many as you need to stabilize your plant; 1 or 2 should do it. Just push them down into the soil close to the post, don't worry about breaking roots, they'll grow back. Then use horticultural wire, strips of cloth or panty hose, string, whatever, to tie the whole package firmly together. If the stakes are sticking way above the moss stick, you can cut them back with a pruner, but you may want to leave some height so your plant can continue to grow taller.
If my size conversion is right, you probably are going to need to repot, also. Like Diana said, don't sink the plant any lower than it now is, you can add potting medium at the bottom to raise the plant up to the proper height. New pot should be only around 5cm larger in diam than old pot.
After you've secured your moss stick/new stakes, just go at it, not really difficult. Support plant with one hand on soil, turn upside down, shake lightly, maybe use a knife to loosen roots from sides of pot if they're sticking. Once root/soil mass is out, gently straighten out roots that are circling the pot, cut long ones so you don't have to fold them up to get them into new pot, work out some of the old soil with your fingers, try a bit of root pruning if you like, and pop the whole thing into its new pot, work new potting medium underneath and around the edges, water well, add more medium if necessary. You know the drill.
Just wanted to thank everyone for their help. I managed to successfully repot the plant! The moss stick wasn't rotting, so I carefully pushed it deeper down the new pot. I also secured it with bamboo canes. It's looking great now! Thanks again! :)